Summary of Significant Accounting Policies (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 property M	Dec. 31, 2010	Dec. 31, 2009
Real Estate Properties
Net reductions to rental income from amortization of capitalized above market and below market leases	$ 8,239	$ 6,895	$ 9,162
Net reductions to income from discontinued operations from amortization of capitalized above market and below market leases	241	553	878
Amortization included in depreciation and amortization	39,102	25,272	23,788
Amortization included in income from discontinued operations	863	1,311	1,346
Future amortization of intangible lease assets and liabilities
2012	48,470
2013	41,908
2014	38,161
2015	32,954
2016	26,904
Thereafter	85,341
Loss on asset impairment	10,355	127,740	15,179
Write down of properties	9,604
Number of properties impaired	26
Depreciation on one property	751
Number of properties depreciated with net book value less than estimated fair value	1
Accrued environmental remediation costs	14,625	16,465
Cash and Cash Equivalents
Maximum original maturity period of cash and short term investments (in months)	3
Other Assets, Net
Deferred financing fees	45,763	40,661
Accumulated amortization for deferred financing fees	16,108	11,459
Deferred leasing costs for properties held and used in operations	130,176	116,959
Accumulated amortization for deferred leasing costs for properties held and used in operations	44,974	42,512
Deferred leasing costs for properties held for sale	0	2,703
Accumulated amortization for deferred leasing costs for properties held for sale	0	1,018
Capitalized lease incentives	16,636	14,716
Accumulated amortization for capitalized lease incentives	1,692	46
Future amortization of deferred financing fees and leasing costs
Future amortization of deferred financing fees and leasing costs, in 2012	21,901
Future amortization of deferred financing fees and leasing costs, in 2013	19,821
Future amortization of deferred financing fees and leasing costs, in 2014	18,249
Future amortization of deferred financing fees and leasing costs, in 2015	15,970
Future amortization of deferred financing fees and leasing costs, in 2016	11,607
Future amortization of deferred financing fees and leasing costs, thereafter	27,309
Future amortization of capitalized lease incentives
Future amortization of capitalized lease incentives, in 2012	1,710
Future amortization of capitalized lease incentives, in 2013	1,710
Future amortization of capitalized lease incentives, in 2014	1,702
Future amortization of capitalized lease incentives, in 2015	1,695
Future amortization of capitalized lease incentives, in 2016	1,691
Future amortization of capitalized lease incentives, thereafter	6,436
Accounting Policy for Derivative Instruments
Fair value of derivative instrument	15,796	6,956
Income Taxes
Minimum percentage of likelihood of realization of tax benefits	50.00%
Foreign currency translation adjustments	11,009	11,641
Above market leases
Real Estate Properties
Capitalized leases for properties held and used in operations	173,909	140,506
Capitalized leases for properties held for sale		6,089
Accumulated amortization of capitalized leases for properties held and used in operations	51,578	55,685
Accumulated amortization of capitalized leases for properties held for sale		5,326
Below market leases
Real Estate Properties
Capitalized leases for properties held and used in operations	101,039	90,483
Capitalized leases for properties held for sale		27
Accumulated amortization of capitalized leases for properties held and used in operations	30,860	24,543
Accumulated amortization of capitalized leases for properties held for sale		20
In place leases
Real Estate Properties
Capitalized leases for properties held and used in operations	299,616	218,006
Capitalized leases for properties held for sale		4,353
Accumulated amortization of capitalized leases for properties held and used in operations	78,030	68,914
Accumulated amortization of capitalized leases for properties held for sale		$ 4,012